1. Field of the Invention
The present invention relates to a car seat mounted in a car.
2. Description of the Related Art
One example of a so-called “active headrest” that moves a headrest to the front side of a car when the car is crashed from its back in order to narrow a gap between a head of a passenger of the car and the headrest is disclosed in Japanese Patent Application (Laid-open) No. 2005-212596.
In the active headrest of this type, a lumbar support mechanism is rotatably supported around an axis that extends in right and left direction within a seat back and is urged to the front side by springs. A load that is applied to the seat back when the passenger suddenly moves to the rear side of the car due to inertia caused when the car is crashed from its back turns the lumbar support mechanism to the back by going against urging force of the springs. Along with that, a pair of pulleys around which a wire whose one end is linked to a lumbar support is wound separates from each other.
Because the pair of pulleys is separated, another end of the wire is largely pulled and thereby, a vertical adjustment mechanism of the headrest linked to the other end of the wire is pulled. Because the vertical adjustment mechanism of the headrest linked to the wire is thus pulled, the vertical adjustment mechanism moves to the seat rear side and by interlocking with this, the headrest moves substantially to the front side of the car.
In the vertical adjustment mechanism described above, pins provided in both right and left ends of a mechanism base portion enter guide holes of a pair of mounting brackets mounted to a back frame. The vertical adjustment mechanism moves in the front-rear direction of the seat as the mechanism base portion elevates in a state when the respective pins are guided by these guide holes.
Therefore, there has been a possibility that the vertical adjustment mechanism causes such an inclination that either one of right and left sides of the vertical adjustment mechanism is positioned under the other side when the vertical adjustment mechanism elevates, due to a difference of frictional resistance between an inner peripheral portion of the respective right and left guide hole and the pins, a dimensional error of each member such as the guide holes, pins, back frame, mounting brackets and others, an error in assembling the pins to the mechanism basal portion, an error in assembling the mounting brackets to the back frame and the like. Such inclination hampers smooth movement of the vertical adjustment mechanism and also smooth movement of the headrest, thus leaving a much room for improvement.